INTERCOMMUNICABILITY 339 



a thing to be accepted as a proved and fundamental proposition. 

 Not only have various workers separately arrived at that conclusion, 

 but the conclusions of the Koyal Commission on Tuberculosis, 1895, 

 included the following words : " We find the present to be a con- 

 venient occasion for stating explicitly that we regard the disease as 

 being the same disease in man and the food animals, no matter though 

 there are differences in the one and the other in their manifesta- 

 tions of the disease ; and that we consider the bacilli of tubercle to 

 form an integral part of the disease in each, and (whatever be its 

 origin) to be transmissible from man to animals, and from animals 

 to animals. Of such transmission there exists a quantity of 

 evidence, altogether conclusive, derived from experiment." * 



Whilst there was up to 1901 almost entire unanimity of opinion 

 amongst various workers in respect to this identity, it should not be 

 supposed that there was unanimity in respect to the degree of 

 pathogenicity. It was, in fact, conceded on all hands that 

 tuberculosis was a more virulent disease in animals than in man, 

 and that the bacillus in the two species differed in various respects 

 as to morphological, biological, and pathological properties (Theobald 

 Smith, Dinwiddie, Frothingham). In 1901, however, Dr Koch 

 expressed the opinion that, " human tuberculosis differs from bovine, 

 and cannot be transmitted to cattle," f and that bovine tuberculosis 

 was scarcely, if at all, transmissible to man. On the same occasion 

 counter-evidence was produced by MacFadyean,J Ravenel, Crook- 

 shank, || and many others. 



As a result of experiment, Koch felt "justified in maintaining that human 

 tuberculosis differs from bovine, and cannot be transmitted to cattle." He further 

 concluded that bovine tuberculosis was scarcely, if at all, transmissible to man. It 

 will be at once obvious that these two conclusions, that human tuberculosis is not 

 transmissible to cattle, and that bovine tuberculosis is not transmissible to man, are 

 of profound and far-reaching importance. Now if it were found on further 

 investigation that these conclusions were correct, the prevention of human 

 tuberculosis would be greatly simplified, and the precautionary measures hitherto 

 adopted for protecting human food from infection with animal tuberculosis need 

 not be enforced with the same stringency as at present, or, at least, would require 

 considerable modification. IT 



* Report of Royal Commission on Tuberculosis, 1895, part i., p. 10, par. 23. 



t Trans. Brit. Cong, on Tuberculosis, 1901, vol. i., p. 29. 



J Ibid., vol. i. , p. 79. 



Ibid., vol. i., p. 91, and vol. iii., p. 553. || Ibid., vol. i., p. 92. 



If It would not necessarily be justifiable to say that in this event such pre- 

 cautionary measures might be " altogether. withdrawn," as has been suggested, for 

 it will be understood that tuberculous meat and milk from animals might still be 

 unwholesome and unfit for the food of man, even though there was evidence 

 to show that the exact specific disease was incommunicable. Presumption would 

 always be against the consumption of meat or milk plus disease products, whether 

 tubercle bacilli or not, for such food is not of the quality and nature reasonably 

 expected by the purchaser. Various non-specific diseases of animals cause meat to 

 be unfit for the food of man. 



